1. Field of the Invention
The invention relates to field refurbishment of slip rings, and in particular to a device and a method for refurbishing, i.e. reconditioning, repairing, or re-working a surface of a slip ring that is a component part of an appliance or machine, with the slip ring remaining in its built-in state in the appliance or machine, specifically in a gantry of a CT scanner (computer tomograph).
2. Description of the Related Art
Slip rings are usually manufactured in a mechanical fabrication workshop and are then built-into an appliance. An appliance of this kind may be, for example, a large machine such as a gantry of a CT scanner. During operation of a slip ring, mechanical wear occurs owing to mechanical friction between a contact brush and a slide track. With slip rings having carbon brushes on metal tracks, abrasion of the carbon brushes alone is substantially greater than abrasion of the slip ring. The carbon brushes are designed so that they can be exchanged relatively easily. However, during a long period of operation, distinct wear of the slip ring itself becomes noticeable. Thus, furrows, grooves, and other cavities may be formed in the surface of a slip ring or its slide tracks. This damage of the surface leads to an increased contact resistance and to an increased wear of the carbon brushes. The same applies in the case of slip rings with metal brushes. Here too, wear of the surface of the slip ring can be observed following an extended period of operation. The damage to the surface may become apparent after a few months or several years, depending upon the operating conditions. Basically, the brushes can be exchanged easily, whilst repair of the slip ring involves relatively large efforts and outlay. Thus, in accordance with the state of the art, a slip ring to be repaired is demounted from the appliance and is machined in a workshop or a manufacturer's fabrication hall, or even replaced with a new slip ring. This has the disadvantage that the appliance is out of operation for a long period of time, and that a relatively time-consuming and laborious exchange of the slip ring must be performed. CT scanners, in particular, must be substantially dismantled for the slip ring to be exchanged. Because the slip rings concerned here, as disclosed in U.S. Pat. No. 4,782,580, have inner diameters of an order of magnitude of 1.5 m and more, it is possible to re-machine them only by means of special and large lathes in specialized workshops.